(Not Applicable)
The present invention relates generally to valves, and more particularly to a uniquely configured valve plug and corresponding seat ring which are specifically configured to mitigate the erosive effects of abrasive fluids flowing within a valve employing linear motion valve trim.
There is currently known in the prior art valves which include shafts and plugs that are linearly displaced during normal operation of the valve. Within these valves, which are often referred to as linear displacement valves, the plug is disposed and movable within a disk stack or valve cage which defines a multiplicity of tortuous or non-tortuous fluid passageways. Certain linear displacement valves are configured for xe2x80x9cover plug flowxe2x80x9d wherein fluid flows radially inward into the interior of the valve cage from the exterior thereof, with the fluid undergoing a pressure drop as a result of the flow through the valve cage. In this arrangement, the valve is opened by lifting the plug off a seat ring which thus allows the fluid to flow from the interior of the valve cage and out of the valve via the unblocked seat ring. Conversely, the movement of the seating surface of the plug into sealed engagement with the complementary seating surface of the seat ring facilitates a closed or shut-off condition for the valve.
Over plug flow linear displacement valves are sometimes employed in applications wherein an erosive fluid (e.g., water with abrasive sand) is channeled therethrough. In these particular applications, when the erosive fluid flows from the outside of the valve cage to the inside thereof and exits the fluid passageways defined by the valve cage, the resultant jets erode the seating surface on the plug. When the eroded plug""s seating angle (defined by its seating surface) makes contact with the seating angle on the seat ring (also defined by its seating surface), valve shut-off is compromised and leakage occurs. The constant leakage of the erosive or abrasive fluid further accelerates the erosion damage between the seat ring and the seating surface of the plug.
The present invention specifically addresses the above-described erosion damage problem by providing a valve plug and seat ring with unique, complementary configurations specifically adapted to either slow the erosive fluid as it passes over the seating surfaces of the plug and seat ring, or alternatively, prevent the fluid jets exiting the valve cage from directly impinging the seating surface of the plug. These, and other features of the present invention, will be described below.
The valve arrangement of the present invention comprises a valve housing, a valve seat and a valve plug. The valve housing defines an interior chamber and a flow opening fluidly communicating with the interior chamber. The interior chamber receives the fluid therein and the flow opening allows the fluid to escape the interior chamber. The seat ring is partially engaged to the valve housing at the flow opening and defines an angled seating surface formed around the seat ring. The seat ring further defines a spaced pair of channels positioned between the seating surface and that portion engaged to the valve housing. The valve plug is axially slidably disposed within the interior chamber and defines a valve plug seating surface and an outer surface. The valve plug seating surface is configured at an angle complementary to that of the seat ring seating surface such that direct engagement of the valve plug seating surface with the seat ring seating surface creates a fluid-tight surface-to-surface seal.
The valve plug further defines a spaced pair of projections positioned between the valve plug seating surface and the outer surface of the valve plug. In a first embodiment, the outer surface partially defines the outer projection. The pair of projections cooperate with respective ones of the channels such that disengagement of the valve plug seating surface from the seat ring seating surface defines a tortuous fluid path. Importantly, the tortuous fluid path reduces the velocity of the fluid as it flows radially inward from the interior housing toward the seating surface of the valve plug prior to its discharge out of the valve arrangement. The reduction in fluidly velocity mitigates erosion of the seating surface of the valve plug by the fluid, thereby minimizing or eliminating the risk of leakage of the valve arrangement when in the closed position.
In the first embodiment, the channels and the projections may each be configured such that the tortuous fluid path defines eight substantially right-angled turns prior to reaching the valve plug seating surface. In a second embodiment, the valve plug seating surface is recessed upwardly into the valve plug relative to the channels. The seat ring seating surface is also disposed upwardly in a complementary orientation to the valve plug seating surface so as to be engageable to the valve plug seating surface. The upwardly disposed seating surfaces prevent direct impingement of the fluid upon the valve plug seating surface when the valve plug is disengaged from the seat ring and the fluid flows radially inward along the tortuous fluid path.
The upwardly disposed seating surfaces further mitigate the erosive effects of the fluid upon the valve plug seating surface in combination with the reduction in erosion effected by the velocity-reducing tortuous fluid path. Additionally, in the second embodiment, the outer one of the pair of projections is spaced inwardly from the outer surface of the valve plug such that the tortuous fluid path defines ten substantially right-angled turns prior to reaching the valve plug seating surface. The increased number of turns of the second embodiment results in an increase in the fluid frictional force within the tortuous fluid path such that the velocity of the fluid may be further reduced.